2021/08/26 更新

写真b

ワダ トオル
和田 亨
WADA Tohru
*大学が定期的に情報更新している項目(その他は、researchmapの登録情報を転載)
所属*
理学部 化学科
理学研究科 化学専攻博士課程後期課程
理学研究科 化学専攻博士課程前期課程
職名*
教授
学位
博士(理学) ( 総合研究大学院大学 )
連絡先
メールアドレス
研究テーマ*
  • 錯体化学。エネルギー・環境問題の観点から大きな注目を集めている燃料電池や人工光合成などのエネルギー変換システムを構築する上で、欠かす事の出来ない電気化学的な酸化還元反応を触媒する遷移金属錯体の開発を行っている。精密にデザインされた錯体を合成し、平衡電位近傍での水の酸化反応や酸素還元反応をめざしている。

  • 研究キーワード
  • 錯体触媒化学

  • 学内職務経歴*
    • 2017年4月 - 現在 
      理学部   化学科   教授
    • 2017年4月 - 現在 
      理学研究科   化学専攻博士課程前期課程   教授
    • 2017年4月 - 現在 
      理学研究科   化学専攻博士課程後期課程   教授
    • 2010年4月 - 2017年3月 
      理学部   化学科   准教授
     

    研究分野

    • ナノテク・材料 / 無機・錯体化学  / 人工光合成

    • ナノテク・材料 / エネルギー化学  / 錯体化学

    経歴

    • 2017年4月 - 現在 
      立教大学   理学部 化学科   教授

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    • 2017年4月 - 現在 
      立教大学   理学研究科 化学専攻博士課程後期課程   教授

      詳細を見る

    • 2017年4月 - 現在 
      立教大学   理学研究科 化学専攻博士課程前期課程   教授

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    • 2010年4月 - 2017年3月 
      立教大学   理学部 化学科   准教授

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    • 2001年4月 - 2010年3月 
      自然科学研究機構   助教

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    学歴

    • 1998年4月 - 2001年3月 
      総合研究大学院大学   数物科学研究科   構造分子科学専攻

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      国名: 日本国

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    • 1996年4月 - 1998年3月 
      学習院大学大学院   自然科学研究科   化学専攻

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      国名: 日本国

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    • 1992年4月 - 1996年3月 
      学習院大学   理学部   化学科

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      国名: 日本国

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    論文

    • Photochemical Water Oxidation Using a Doubly N-Confused Hexaphyrin Dinuclear Cobalt Complex 査読有り

      Takashi Nakazono, Tohru Wada

      INORGANIC CHEMISTRY60 ( 3 ) 1284 - 1288   2021年2月

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      担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      A doubly N-confused hexaphyrin dinuclear cobalt complex (Co2DNCH) is revealed as an efficient water oxidation catalyst, outperforming the mononuclear cobalt porphyrin with the same aryl group as those in Co2DNCH. By photoirradiation of a water/acetone-d(6) (9:1) mixture containing Co2DNCH, [Ru-II(bpy)(3)](2+), and S2O82- as the water oxidation catalyst, photosensitizer, and sacrificial electron acceptor, respectively, with visible light, O-2 was obtained as the maximum with turnover number = 1200, turnover frequency = 3.9 s(-1), and quantum yield = 0.30.

      DOI: 10.1021/acs.inorgchem.0c02602

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    • Preparation and characterization of a μ-P2O7-μ-HPO4 dinuclear Fe2(III, III) complex 査読有り

      Miyazato, Yuji, Imaizumi, Kouta, Tanaka, Rikako, Wada, Tohru, Matsushita, Nobuyuki

      Bulletin of the Chemical Society of Japan91 ( 5 ) 787 - 789   2018年5月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      The [{Fe(Me3tacn)}2(μ-P2O7)(μ-HPO4)].bul.12H2O dinuclear Fe2(III,III) complex was prepd.(Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane). The HPO4 2- bridge in the complex arises from hydrolysis of the pyrophosphate bound to the Fe(III) centers in the trinuclear [{Fe(Me3tacn)}3 -(P2O7)2]+ intermediate. Electrochem. redn. of this complex at pH <3.2 results in dissocn. of the H2PO4 - bridge.

      DOI: 10.1246/bcsj.20170427

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    • Mechanism of Water Oxidation Catalyzed by a Dinuclear Ruthenium Complex Bridged by Anthraquinone 招待有り 査読有り

      Tohru Wada, Shunsuke Nishimura, Taro Mochizuki, Tomohiro Ando, Yuji Miyazato

      CATALYSTS7 ( 2 ) 56/1 - 56/16   2017年2月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI AG  

      We synthesized 1,8-bis(2,2':6',2"-terpyrid-4'-yl)anthraquinone (btpyaq) as a new dimerizing ligand and determined its single crystal structure by X-ray analysis. The dinuclear Ruthenium complex [Ru-2(mu-Cl)(bpy)(2)(btpyaq)](BF4)(3) ([3](BF4)(3), bpy = 2,2'-bipyridine) was used as a catalyst for water oxidation to oxygen with (NH4)(2)[Ce(NO3)(6)] as the oxidant (turnover numbers = 248). The initial reaction rate of oxygen evolution was directly proportional to the concentration of the catalyst and independent of the oxidant concentration. The cyclic voltammogram of [3](BF4)(3) in water at pH 1.3 showed an irreversible catalytic current above +1.6 V (vs. SCE), with two quasi-reversible waves and one irreversible wave at E-1/2 = +0.62, +0.82 V, and E-pa = +1.13 V, respectively. UV-vis and Raman spectra of [3](BF4)(3) with controlled-potential electrolysis at +1.40 V revealed that [Ru(IV)=O O=Ru(IV)](4+) is stable under electrolysis conditions. [Ru(III), Ru(II)] species are recovered after dissociation of an oxygen molecule from the active species in the catalytic cycle. These results clearly indicate that an O-O bond is formed via [Ru(V)=O O=Ru(IV)](5+).

      DOI: 10.3390/catal7020056

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    • Synthesis and Characterization of an Ru-2(III, IV) Complex Containing Pyrophosphate Bridge 査読有り

      Yuji Miyazato, Tohru Wada, Masaaki Ohba, Nobuyuki Matsushita

      CHEMISTRY LETTERS45 ( 12 ) 1388 - 1390   2016年12月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      We prepared a new Ru-2(III, IV) complex containing a pyrophosphate as the dinucleating component, by the reaction between the mononuclear complex [Ru(Me(3)tacn)Cl-3] and Na4P2O7 center dot 10H(2)O in aqueous solution. Cyclic voltammetric measurement for the complex [{Ru(Me(3)tacn)}(2)(mu-O)(mu-P2O7)]PF6 (1) in aqueous solution revealed the formation of two species with higher oxidation states, such as [O=Ru(IV)Ru(IV)=O] and [O=Ru(IV)Ru(V)=O](+). Furthermore, this complex showed activity for water oxidation reaction with Ce(NH4)(2)(NO3)(6) as the chemical oxidant in acidic aqueous solution.

      DOI: 10.1246/cl.160721

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    • Water Oxidation Catalyzed by a Ruthenium Complex with an Ru-C Bond 査読有り

      Tohru Wada, Takahide Hiraide, Yuji Miyazato

      CHEMISTRYSELECT1 ( 12 ) 3045 - 3048   2016年8月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

      We prepared a new Ru(III) complex with a covalent bond between the central Ru and C of the ligand, [RuCl(dpp)(bpy)] Cl ([1] Cl, dpp= 2,6-dipyridylphenyl, bpy= 2,2'-bipyridine), through the reaction of [(eta(6)-C6H6) RuCl(bpy)] Cl with one equivalent of 1,3-di(pyrid-2-yl) benzene. X-ray analysis of a single crystal of [1](PF6), which was prepared via the anion exchange of [1] Cl, revealed the short Ru-C bond length of [1](+). [1] Cl was easily hydrolyzed in a neutral water solution to the hydroxo complex, [Ru(OH)(dpp)(bpy)](+) ([2](+)). Cyclic voltammetry of [1]+ showed that the Ru(II)/ Ru(III) potential of [1](+) was more negative than that of the 2,2': 6', 2"-terpyridine (trpy) analogue, [RuCl(bpy)(trpy)](ClO4), by -770 mV under the same conditions. Moreover, the Ru(V)= O species, which is a key intermediate of water oxidation, was produced by electrochemical oxidation of [2](+) at an extremely negative potential (+ 0.80 V vs. saturated calomel electrode). [2](+) catalyzed water oxidation at pH 2.5 with [Ru (bpy)(3)](3+) as the oxidant. 2,6-dipyridylphenyl as a strong s-electron donor ligand negatively shifted the oxidation potential of water.

      DOI: 10.1002/slct.201600716

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    • Synthesis and characterization of a di-μ-oxalato tetracopper(II) complex with tetranucleating macrocyclic ligand 査読有り

      Miyazato, Yuji, Asato, Eiji, Ohba, Masaaki, Wada, Tohru

      Bulletin of the Chemical Society of Japan89 ( 4 ) 430 - 436   2016年4月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      A tetracopper(II) complex contg. two oxalate anions in the metal-based host cavity, [Cu4(Lpy)(μ-ox)2](PF6).2(2-PrOH) (1), where ox2- is oxalato (C2O4 2-), was prepd. by reacting H2Lpy, a phenol-based tetranucleating macrocyclic ligand with four pyridylmethyl pendant arms, Cu(ClO4)·6H2O, and sodium oxalate (1:4:2 stoichiometry, resp.) in methanol, followed by exchange of the counteranion with excess of NH4PF6. Single-crystal x-ray diffraction of 1 revealed that two {Cu(II)Cu(II)} units, bridged by a phenolato group of Lpy2-, were connected by two oxalato anions, to construct a rectangular {CuCu}(μ-ox)2{CuCu} tetranuclear framework. This rectangular framework was maintained in DMF soln. The magnetic measurement of 1 in the 2-300 K range revealed antiferromagnetic behavior. The antiferromagnetic interaction in this complex occurs between the Cu(II) centers bridged by an oxalate (J = -140 cm-1).

      DOI: 10.1246/bcsj.20150338

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    • Homogeneous Photocatalytic Water Oxidation with a Dinuclear Co-III-Pyridylmethylamine Complex 査読有り

      Tomoya Ishizuka, Atsuko Watanabe, Hiroaki Kotani, Dachao Hong, Kenta Satonaka, Tohru Wada, Yoshihito Shiota, Kazunari Yoshizawa, Kazuaki Ohara, Kentaro Yamaguchi, Satoshi Kato, Shunichi Fukuzumi, Takahiko Kojima

      INORGANIC CHEMISTRY55 ( 3 ) 1154 - 1164   2016年2月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      A bis-hydroxo-bridged dinuclear Co-III-pyridylmethylamine complex (1) was synthesized and the crystal structure was determined by X-ray crystallography. Complex 1 acts as a homogeneous catalyst for visible-light-driven water oxidation by persulfate (S2O82-) as an oxidant with [Ru-II(bpy)(3)](2+) (bpy = 2,2'-bipyridine) as a photosensitizer affording a high quantum yield (44%) with a large turnover number (TON = 742) for O-2 formation without forming catalytically active Co-oxide (CoOx) nanoparticles. In the water-oxidation process, complex 1 undergoes proton-coupled electron-transfer (PCET) oxidation as a rate-determining step to form a putative dinuclear bis-mu-oxyl Co-III complex (2), which has been suggested by DFT calculations. Catalytic water oxidation by 1 using [Ru-III(bpy)(3)](3+) as an oxidant in a (H2O)-O-16 and (H2O)-O-18 mixture was examined to reveal an intramolecular O-O bond formation in the two-electron-oxidized bis-mu-oxyl intermediate, prior to the O-2 evolution.

      DOI: 10.1021/acs.inorgchem.5b02336

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    • Reversible Structural Changes Accompanying the Two-Electron Redox Reaction of Pt(tacn) (tacn: 1,4,7-triazacyclononane) Complexes 査読有り

      Tohru Wada, Koki Enami, Ryohei Kojima, Tomoki Okada, Yuki Ishikawa, Yuji Miyazato, Ernst Horn, Yuji Mochizuki

      BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN88 ( 9 ) 1230 - 1237   2015年9月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Platinum complexes with 1,4,7-triazacyclononane (tacn) as facial ligands, [(PtCl3)-Cl-Iv(tacn)](ClO4), [(PtCl)-Cl-Iv(bpy)-(tacn)](ClO4)(3) ([1](ClO4), and [2](ClO4)(3), bpy: 2,2'-bipyridine) were prepared, and their hexa-coordinated octahedral structures were determined via single-crystal X-ray analysis. In aqueous solutions containing NaCl as the electrolyte, [2](3+) exhibited a quasi-reversible two-electron redox wave at +0.22 V (vs. SCE) with a large peak separation Delta E = E-pc - E-pa = 0.28 V). In addition, controlled-potential reduction of [2](3+) at -0.30 V in aqueous solutions containing NaCl afforded [Pt-II(bpy)(tacn)](2+) ([3](2+)), which was then re-oxidized to regenerate [2](3+). X-ray analysis of [3](2+) revealed a tetra-coordinated square-planar structure in which both tacn and bpy were bound to the central Pt as bidentate ligands. The redox potential of this reaction is coupled with dissociation/association of Cl- from/to Pt in the solution. MO/DFT calculations indicate that structural changes in tacn promote the reversible two-electron redox reaction between the octahedral Pt(IV) and square planar Pt(II) complexes.

      DOI: 10.1246/bcsj.20150097

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    • Four-electron reduction of dioxygen catalysed by dinuclear cobalt complexes bridged by bis(terpyridyl)anthracene 査読有り

      Tohru Wada, Hidetaka Maki, Tomoyuki Imamoto, Hirokazu Yuki, Yuji Miyazato

      CHEMICAL COMMUNICATIONS49 ( 39 ) 4394 - 4396   2013年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

      Dinuclear cobalt-1,10-phenanthroline (1) and 2,2'-bipyridine (2) complexes bridged by 1,8-bis(2,2':6',2 ''-terpyrid-4'-yl)anthracene (btpyan) were prepared. Both of the complexes selectively catalysed the electrochemical four-electron reduction of dioxygen to H2O without the generation of H2O2 as a two-electron reduction product.

      DOI: 10.1039/c2cc36528f

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    • Synthesis and characterization of a tetracopper(II) complex having a [Cu4(μ4-O)] framework stabilized by the tetranucleating macrocyclic ligand 査読有り

      Miyazato, Yuji, Asato, Eiji, Ohba, Masaaki, Wada, Tohru

      Bulletin of the Chemical Society of Japan85 ( 8 ) 895 - 901   2012年8月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      A tetranucleating macrocyclic ligand bearing four acetate pendants, L6-, was newly yielded by a stepwise synthesis from [Zn4(L')(AcO)2(OH)2](ClO4)2·H2O (1), which was prepd. from [2 + 2] Schiff-base condensation of 2,6-diformyl-4-methylphenol and 1,2-bis(2-aminoethoxy)ethane in the presence of Zn(ClO4)2·6H2O, sodium acetate, and triethylamine. A μ4-oxo tetracopper(II) complex [Cu4(L)(μ4-O)]·H2O (2) was obtained from the reaction of Cu(ClO4)2·6H2O and Na2H4L in methanol under basic conditions, and characterized by x-ray crystallog. Two adjacent copper centers were bridged by the phenoxo oxygen of L6- to form [Cu2(μ-OPh)] unit, two pairs of which were further linked by an oxo anion with a distorted tetrahedral geometry, finally creating a tetracopper core [{Cu2(μ-OPh)}2(μ4-O)]. Cryomagnetic measurements of 2 at 2-300 K exhibited antiferromagnetic behavior. Magnetic anal. of 2 was carried out by the four spin-exchange interactions model based on the bridging mode and the Cu-(μ4-O)-Cu angles, JA: Cu1/Cu4, JB: Cu2/Cu3, JC: Cu1/Cu2 and Cu3/Cu4, and JD: Cu1/Cu3 and Cu2/Cu4 pairs. The estd. four magnetic exchange interactions (JA, JB, JC, and JD) were -17, -161, -108, and -109 cm-1, resp.

      DOI: 10.1246/bcsj.20120084

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    • Catalytic Four-Electron Oxidation of Water by Intramolecular Coupling of the Oxo Ligands of a Bis(ruthenium-bipyridine) Complex 査読有り

      Tohru Wada, Hideki Ohtsu, Koji Tanaka

      CHEMISTRY-A EUROPEAN JOURNAL18 ( 8 ) 2374 - 2381   2012年2月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

      A bis(rutheniumbipyridine) complex bridged by 1,8-bis(2,2':6',2''-terpyrid-4'-yl)anthracene (btpyan), [Ru2(mu-Cl)(bpy)2(btpyan)](BF4)3 ([1](BF4)3; bpy=2,2'-bipyridine), was prepared. The cyclic voltammogram of [1](BF4)3 in water at pH 1.0 displayed two reversible [RuII,RuII]3+/[RuII,RuIII]4+ and [RuII,RuIII]4+/[RuIII,RuIII]5+ redox couples at E1/2(1)=+0.61 and E1/2(2)=+0.80 V (vs. Ag/AgCl), respectively, and an irreversible anodic peak at around E=+1.2 V followed by a strong anodic currents as a result of the oxidation of water. The controlled potential electrolysis of [1]3+ ions at E=+1.60 V in water at pH 2.6 (buffered with H3PO4/NaH2PO4) catalytically evolved dioxygen. Immediately after the electrolysis of the [1]3+ ion in H216O at E=+1.40 V, the resultant solution displayed two resonance Raman bands at $\tilde \nu $=442 and 824 cm-1. These bands shifted to $\tilde \nu $=426 and 780 cm-1, respectively, when the same electrolysis was conducted in H218O. The chemical oxidation of the [1]3+ ion by using a CeIV species in H216O and H218O also exhibited the same resonance Raman spectra. The observed isotope frequency shifts (?$\tilde \nu $=16 and 44 cm-1) fully fit the calculated ones based on the Ru?O and O?O stretching modes, respectively. The first successful identification of the metal?O?O?metal stretching band in the oxidation of water indicates that the oxygenoxygen bond at the stage prior to the evolution of O2 is formed through the intramolecular coupling of two Ruoxo groups derived from the [1]3+ ion.

      DOI: 10.1002/chem.201102236

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    • A new type of electrochemical oxidation of alcohols mediated with a ruthenium-dioxolene-amine complex in neutral water 査読有り

      Hironobu Ozawa, Takami Hino, Hideki Ohtsu, Tohru Wada, Koji Tanaka

      INORGANICA CHIMICA ACTA366 ( 1 ) 298 - 302   2011年1月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

      Electrochemical oxidation of [Ru-II(terpy)(sq)(NH3)](+) in neutral water (pH 8.0) at +0.8 V (versus SCE) generated [Ru-II(terpy)(q)(NH2 center dot)](2+) and/or [Ru-III(terpy)(sq)(NH2 center dot)](2+) (terpy = 2,2':6',2 ''-terpyridine, sq = 3,5-di-tert-butyl-1,2-semiquinonate, q = 3,5-di-tert-butyl-1,2-benzoquinone), which played roles in hydrogen abstraction and one-electron acceptor in the catalytic oxidation of methanol, ethanol, and 2-propanol affording formaldehyde, acetoaldehyde, and acetone, respectively, under the electrolysis conditions. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

      DOI: 10.1016/j.ica.2010.11.013

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    • Substituents dependent capability of bis(ruthenium-dioxolene-terpyridine) complexes toward water oxidation 招待有り 査読有り

      Tohru Wada, James T. Muckerman, Etsuko Fujita, Koji Tanaka

      DALTON TRANSACTIONS40 ( 10 ) 2225 - 2233   2011年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

      The bridging ligand, 1,8-bis(2,2':6',2 ''-terpyrid-4'-yl)anthracene (btpyan) was synthesized by the Miyaura-Suzuki cross coupling reaction of anthracenyl-1,8-diboronic acid and 4'-triflyl-2,2': 6'-2 ''-terpyridine in the presence of Pd(PPh3)(4) (5 mol%) with 68% in yield. Three ruthenium-dioxolene dimers, [Ru-2(OH)(2)(dioxolene)(2)(btpyan)](0) (dioxolene = 3,6-di-tert-butyl-1,2-benzosemiquinone ([1](0)), 3,5-dichloro-1,2-benzosemiquinone ([2](0)) and 4-nitro-1,2-benzosemiquinone ([3](0))) were prepared by the reaction of [Ru2Cl6(btpyan)](0) with the corresponding catechol. The electronic structure of [1](0) is approximated by [Ru-2(II)(OH)(2)(sq)(2)(btpyan)](0) (sq = semiquinonato). On the other hand, the electronic states of [2](0) and [3](0) are close to [Ru-2(III)(OH)(2) (cat)(2)(btpyan)](0) (cat = catecholato), indicating that a dioxolene having electron-withdrawing groups stabilizes [Ru-2(III)(OH)(2)(cat)(2)(btpyan)](0) rather than [Ru-2(II)(OH)(2)(sq)(2)(btpyan)](0) as resonance isomers. No sign was found of deprotonation of the hydroxo groups of [1](0), whereas [2](0) and [3](0) showed an acid-base equilibrium in treatments with t-BuOLi followed by HClO4. Furthermore, controlled potential electrolysis of [1](0) deposited on an ITO (indium-tin oxide) electrode catalyzed the four-electron oxidation of H2O to evolve O-2 at potentials more positive than +1.6 V (vs. SCE) at pH 4.0. On the other hand, the electrolysis of [2](0) and [3](0) deposited on ITO electrodes did not show catalytic activity for water oxidation under similar conditions. Such a difference in the reactivity among [1](0), [2](0) and [3](0) is ascribed to the shift of the resonance equilibrium between [Ru-2(II)(OH)(2)(sq)(2)(btpyan)](0) and [Ru-2(III)(OH)(2)(cat)(2)(btpyan)](0).

      DOI: 10.1039/c0dt00977f

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    • Redox Behavior of Ruthenium(Bipyridine)(Terpyridine)(Carbonyl) Complex-modified Carbon Electrode and Reactivity toward Electrochemical Reduction of CO2 査読有り

      Yuhei Tsukahara, Tohru Wada, Koji Tanaka

      CHEMISTRY LETTERS39 ( 11 ) 1134 - 1135   2010年11月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Electrochemical reduction of a diazonium complex [Ru-(bpy)(trpy-ph-N-2(+))(CO)](PF6)(3) ([1](PF6)(3)) (bPY = dine, trpy-ph-N-2(+) = 4-(2,2' 6',2"-terpyncline-4'-yl)benzenedi-azonium) using a GC electrode forms multdayer films of the complexes on the electrode surface, on which the reduced form of the complex showed strong affinity toward CO2

      DOI: 10.1246/cl.2010.1134

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    • Formation and Structure of an (Iminium ion)ruthenium Complex and Reaction of the Iminium Ion Moiety with Alcohols 査読有り

      Sohei Fukui, Noriyuki Suzuki, Tohru Wada, Koji Tanaka, Hirotaka Nagao

      ORGANOMETALLICS29 ( 7 ) 1534 - 1536   2010年4月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      The (iminium ion)ruthenium(II) complex mer(Cl, Cl,Cl)-[RuCl3{eta(2)-NCHCH(2)py(C(2)H(4)py)C2H5}] was synthesized via a C-H activation of the bridging ethyl group of an ethylbis(2-pyridylethyl)amine ligand and characterized by X-ray structural analysis. Oxidations of alcohols by the (iminium ion)ruthenium(11) complex occurred with generation of mer-[(RuCl3)-Cl-III(ebpea)].

      DOI: 10.1021/om100161r

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    • Photoinduced four- and six-electron reduction of mononuclear ruthenium complexes having NAD(+) analogous ligands 査読有り

      Takashi Fukushima, Tohru Wada, Hideki Ohtsu, Koji Tanaka

      DALTON TRANSACTIONS39 ( 48 ) 11526 - 11534   2010年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

      The ruthenium complexes [Ru(bpy)(pbn)(2)](PF6)(2) ([2](2+); bpy = 2,2'-bipyridine, pbn = 2-(2-pyridyl)benzo[b]-1,5-naphthyridine) and [Ru(pbn)(3)](PF6)(2) ([3](2+)) were synthesized. Photoirradiation (lambda > 420 nm) of [2](2+) and [3](2+) in CH3CN/triethanolamine (TEOA) brought about proton coupled four-and six-electron reduction of the complexes to produce [Ru(bpy)(pbnH(2))(2)](PF6)(2) ([2.H-4](2+); pbnH(2) = 5,10-dihydro-2-(2-pyridyl)benzo[b]-1,5-naphthyridine) and [Ru(pbnH(2))(3)](PF6)(2) ([3.H-6](2+)), respectively. The photoexcited [Ru-III(bpy)(pbn(center dot-))(pbnH(2))](2+) intermediate is quenched by intermolecular electron transfer from TEOA to Ru-III, while intramolecular transfer from pbnH(2) to Ru-III is negligible. As a result, novel photochemical four-and six-electron reduction of [2](2+) and [3](2+) is achieved through repetition of the two-electron reduction of the Ru-pbn group. The high efficiency photochemical two-, four- and six-electron reductions of [Ru(bpy)(2)(pbn)](2+) ([1](2+)), [2](2+) and [3](2+), respectively, by taking advantage of proton coupled two electron reduction of NAD(+) analogous type ligands such as pbn opens a general pathway for multi-electron reduction of metal complexes via illumination with visible light.

      DOI: 10.1039/c0dt00504e

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    • Photochemical Stereospecific Hydrogenation of a Ru Complex with an NAD(+)/NADH-Type Ligand 査読有り

      Takashi Fukushima, Etsuko Fujita, James T. Muckerman, Dmitry E. Polyansky, Tohru Wada, Koji Tanaka

      INORGANIC CHEMISTRY48 ( 24 ) 11510 - 11512   2009年12月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      A polypyridylruthenium complex with an NAD(+)/NADH model ligand, [Ru(bpy)(2)(pbn)](2+) [bpy = 2,2'-bipyridine, pbn = 2-(2-pyridyl)benzo[b]-1,5-naphthyridine] in a D2O/CH3CN/triethylamine solution, undergoes stereospecific hydrogenation to give Delta-(S)- and Lambda-(R)- [Ru(bpy)(2)(pbnDD)](2+) [pbnDD = 5,10-dideutero-2-(2-pyridyl)benzo[b]-1,5-naphthyridine] upon visible-light irradiation. This result clearly indicates the pathway via the pi-stacked dimer of the deuterated one-electron-reduced species. The reduction of [Ru(bpy)(2)(pbn)](2+) with Na2S2O4 in D2O did not afford any stereospecific products. Furthermore, the more sterically crowded Ru complex, [Ru(dmb)(2)(pbn)](2+) (dmb = 6,6'-dimethyl-2,2'-bipyridine), did not produce the corresponding pbnDD species upon irradiation.

      DOI: 10.1021/ic901935u

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    • Characterization of Redox States of Ru(OH2)(Q)(tpy)2+ (Q = 3,5-di-tert-butyl-1,2-benzoquinone, tpy = 2,2':6',2''-terpyridine) and Related Species through Experimental and Theoretical Studies (共著) 査読有り

      Tsai, M.-K, Rochford, J, Polyansky, D. E, Wada, T, Tanaka, K, Fujita, E, M

      Inorganic Chemistry48 ( 10 ) 4372 - 4383   2009年5月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

      The redox states of Ru(OH2)(Q)(tpy)2+ (Q = 3,5-di-tert-butyl-1,2-benzoquinone, tpy = 2,2':6',2''-terpyridine) are studied through exptl. and theor. UV-visible spectra and Pourbaix diagrams. The electrochem. properties are reported for the species resulting from deprotonation and redox processes in aq. soln. The formal oxidn. states of the redox couples in the various intermediate complexes are systematically assigned using electronic structure theory. The controversy over the electronic assignment of ferromagnetic vs. antiferromagnetic coupling was studied through comparison of ab initio methods and the broken-symmetry d. functional theory (DFT) approach. The various pKa values and redn. potentials, including the consideration of proton-coupled electron-transfer (PCET) processes, are calcd., and the theor. version of the Pourbaix diagram is constructed to elucidate and assign several previously ambiguous regions in the exptl. diagram.

      DOI: 10.1021/ic900057y

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    • Water Oxidation by a Ruthenium Complex with Non-Innocent Quinone Ligands: Possible Formation of an O-O Bond at a Low Oxidation State of the Metal.(共著) 査読有り

      Muckerman, J. T, Polyansky, D, Wada, T, Tanaka, K, Fujita, E

      Inorganic Chemistry47 ( 6 ) 1787 - 1802   2008年3月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

      Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru2(OH)2(3,6-Bu2Q)2(btpyan)](SbF6)2 (3,6-Bu2Q = 3,6-ditert-butyl-1,2-benzoquinone, btpyan = 1,8-bis(2,2':6',2''-terpyrid-4'-yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for H2O oxidn. when immobilized on an In-Sn-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogs with the bpy ligand (bpy = 2,2'-bipyridine) replacing quinone, are summarized here together with new theor. and exptl. results that show striking features for both the dinuclear and mononuclear species. The identity and oxidn. state of key mononuclear species, including the previously reported oxyl radical, were reassigned. The gas-phase theor. calcns. indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and H2O moiety are involved in redox reactions throughout the entire catalytic cycle for H2O oxidn. The theor. study identifies [Ru2(O2 -)(Q-1.5)2(btpyan)] as a key intermediate and the most reduced catalyst species that is formed by removal of all 4 protons before 4-electron oxidn. takes place. While the study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic studies, and key issues and challenges in H2O oxidn. with the Tanaka catalyst (and its analogs with Cl- or NO2-substituted quinones and a species with a xanthene bridge instead an anthracene) are discussed.

      DOI: 10.1021/ic701892v

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    • Electrochemical and photochemical behavior of a ruthenium(II) complex bearing two redox sites as a model for the NAD+/NADH redox couple. (共著) 査読有り

      Tannai, H, Koizumi, T.-a, Wada, T, Tanaka, K

      Angewndte Chemie, International Edition46 ( 37 ) 7112 - 7115   2007年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley-VCH Verlag GmbH & Co. KGaA  

      The mononuclear Ru(II) complex, [Ru(bbnp)(terp)]2+ (bbnp = 2,6-bis(benzo[b]-1,5-naphthyridin-6-yl)-4-tert-butylpyridine and terpy = 2,2:6',2''-terpyridine) is reversibly converted into the 4-electron-reduced form [1-H4]2+ through electrochem. and photochem. redox reactions in aq. soln. The 2,6-bis(benzo[b]-1,5-naphthyridin-6-yl)-4-tert-butylpyridine ligand acts alternatively as a reservoir/source of 4 electrons or 4 protons.

      DOI: 10.1002/anie.200701204

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    • Generation of a RuII-semiquinone-anilino-radical complex through the deprotonation of a RuIII-semiquinone-anilino complex. (共著) 査読有り

      Miyazato, Y, Wada, T, Muckerman, J. T, Fujita, E, Tanaka, K

      Angewndte Chemie, International Edition46 ( 30 ) 5728 - 5730   2007年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      DOI: 10.1002/anie.200701600

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    • Generation of a RuII-semiquinone-anilino-radical complex through the deprotonation of a RuIII-semiquinone-anilino complex. (共著) 査読有り

      Miyazato, Y, Wada, T, Muckerman, J. T, Fujita, E, Tanaka, K

      Angewndte Chemie, International Edition46 ( 30 ) 5728 - 5730   2007年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley-VCH Verlag GmbH & Co. KGaA  

      Aminyl radicals may one day be useful oxidn. catalysts if their thermodn. instability can be overcome, for example, through complexation with a metal. Deprotonation of the semiquinonato-anilido complex [RuIII(NHPh-bpa)(tBu2sq)]+ (1; NHPh-bpa = 2-(bis(pyridylmethyl)aminomethyl)-anilido ligand; tBu2sq- = 3,5-di-tert-butylsemiquinonate) leads to formation of the semiquinonato-anilino-radical complex [RuII(·NPh-bpa)(tBu2sq)] (2). Electrochem. redn. of 2 leads to formation of the catecholato-anilino radical complex [RuII(·NPh-bpa)(tBu2cat)]- (3). Treatment of 1 with MeSO3H gave the semiquinone-aniline complex [RuIII(NH2Ph-bpa)(tBu2sq)]2+ (4). The complexes were studied using cyclic voltammetry, EPR, magnetic susceptibility and DFT calcns.

      DOI: 10.1002/anie.200701600

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    • Photochemical and radiolytic production of an organic hydride donor with a RuII complex containing an NAD+ model ligand. (共著) 査読有り

      Polyansky, D, Cabelli, D, Muckerman, J. T, Fujita, E, Koizumi, T.-a, Fukushima, T, Wada, T, Tanaka, K

      Angewndte Chemie, International Edition46 ( 22 ) 4169 - 4172   2007年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley-VCH Verlag GmbH & Co. KGaA  

      The photochem. and electrochem. properties of a polypyridylruthenium complex with an NAD+/NADH (NAD+ = NAD) model ligand, [Ru(bpy)2-(pbn)]2+ ([1]2+; bpy = 2,2'-bipyridine, pbn = 2-(2-pyridyl)benzo[b]-1,5-naphthyridine), were investigated. When solns. contg. [1]2+ and triethylamine are irradiated with visible light, [(1)HH]2+ is produced cleanly.

      DOI: 10.1002/anie.200700304

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    • Experimental and Theoretical Evaluation of the Charge Distribution over the Ruthenium and Dioxolene Framework of [Ru(OAc)(dioxolene)(terpy)] (terpy = 2,2':6',2''-terpyridine) Depending on the Substituents. (共著) 査読有り

      Wada, T, Yamanaka, M, Fujihara, T, Miyazato, Y, Tanaka, K

      Inorganic Chemistry45 ( 22 ) 8887 - 8894   2006年12月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Novel platinum-ruthenium dinuclear complex bridged by 2-aminoethanethiol 査読有り

      Rei Okamura, Tohru Wada, Koji Tanaka

      BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN79 ( 10 ) 1535 - 1540   2006年10月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      A platinum-ruthenium dinuclear complex, [(PtCl){RuCl((t)Bu(2)sq)}(btpyxa)](2+) ([2](2+)) (btpyxa = 2,7-di-tert-butyl-9.9-dimethyl-4,5-bis(2,2':6',2 ''-terpyrid-4'-yl)xanthene, (t)Bu(2)sq = 3,5 -di-tert-butyl-1,2-benzosemiquinonateion), in which btpyxa acts as a bridging ligand, was prepared, and its physical properties were compared to those of an analogous dmso complex, [(PtCl){Ru((t)Bu(2)sq)(dmso)}(btpyxa)](2+) ([1](2+)) (dmso = dimethyl sulfoxide). Treatment of complex [1](2+) with an aqueous NaOH solution followed by 2-aminoethanethiol afforded [{Pt(SCH2CH2NH2)}{Ru((t)Bu(2)sq)(dmso))(btpyxa)](2+) ([3](2+)). On the other hand, the reaction of complex [2](2+) with 2-arninoethanethiol produced [{Pt(SCH2CH2NH2)}Ru((t)Bu(2)sq)}(btpyxa)](2+) ([4](2+)), in which Pt and Ru atoms are bridged by the 2-aminoethanethiolato ligand. Complex [4](2+) was also obtained by heating complex [3](2+) in 2-methoxyethanol.

      DOI: 10.1246/bcsj.79.1535

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    • Experimental and Theoretical Evaluation of the Charge Distribution over the Ruthenium and Dioxolene Framework of [Ru(OAc)(dioxolene)(terpy)] (terpy = 2,2':6',2''-terpyridine) Depending on the Substituents. (共著) 査読有り

      Wada, T, Yamanaka, M, Fujihara, T, Miyazato, Y, Tanaka, K

      Inorganic Chemistry45 ( 22 ) 8887 - 8894   2006年10月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

      Ru complexes [Ru(OAc)(dioxolene)(terpy)] having various substituents on the dioxolene ligand (dioxolene = 3,5-t-Bu2C6H2O2 (1), 4-t-BuC6H3O2 (2), 4-ClC6H3O2 (3), 3,5-Cl2C6H2O2 (4), Cl4C6O2 (5); terpy = 2,2&#039;:6&#039;2&#039;&#039;-terpyridine) were prepd. EPR spectra of these complexes in glassy frozen solns. (CH2Cl2:MeOH = 95:5, vol./vol.) at 20 K showed anisotropic signals with g tensor components 2.242 &gt; g1 &gt; 2.104, 2.097 &gt; g2 &gt; 2.042, and 1.951 &gt; g3 &gt; 1.846. An anisotropic value, Δg = g1-g3, and an isotropic g value, 〈g〉 = [(g1 2 + g2 2 + g3 2)/3]1/2, increase in the order 1 &lt; 2 &lt; 3 &lt; 4 &lt; 5. The resonance between the RuII(sq) (sq = semiquinone) and RuIII(cat) (cat = catecholato) frameworks shifts to the latter with an increase of the no. of electron-withdrawing substituents on the dioxolene ligand. DFT calcns. of 1, 2, 3, and 5 also support the increase of the Ru spin d. (RuIII character) with an increase of the no. of Cl atoms on the dioxolene ligand. The singly occupied MOs (SOMOs) of 1 and 5 are very similar to each other and stretch out the Ru-dioxolene frameworks, whereas the LUMO of 5 is localized on Ru and two O atoms of dioxolene in comparison with that of 1. Electron-withdrawi

      DOI: 10.1021/ic060696i

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    • Redox behavior and catalytic oxidation reactions of alcohols by a new ruthenium(III)-dioxolene-amine complex of bis(2-pyridylmethyl)-2-aminoethylamine 査読有り

      Yuji Miyazato, Tohru Wada, Koji Tanaka

      BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN79 ( 5 ) 745 - 747   2006年5月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      A ruthenium-dioxolene-amine complex, [Ru-III(NH2L)(Bu(2)sq)](PF6)(2)center dot 0.5H(2)O (NH2-L = bis(2-pyridylmethyl)2-aminoethylamine, Bu(2)sq(-) = 15-di-tert-butylsemiquinonate). was newly prepared. The complex undergoes spontaneous one-electron reduction under basic conditions in MeOH and works as an electrocatalyst in the oxidation of benzyl alcohol to benzaldehyde under electrolysis at +0.4V (vs SCE).

      DOI: 10.1246/bcsj.79.745

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    • Comparison of basicity of the diimine and quinoid group of 1,10-phenanthroline-5,6-dione ligated on Pt(II) 査読有り

      R Okamura, T Fujihara, T Wada, K Tanaka

      BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN79 ( 1 ) 106 - 112   2006年1月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      A platinum(II) complex bearing 1,10-phenanthroline-5,6-dione (phenO(2)), [PtCl(phenO(2)-N,N')(PPh3)](+) ([2](+)) was newly prepared and characterized. An X-ray crystallographic study of [2](PF6) revealed that the phenO(2) ligand coordinates to platinum with the N,N'-chelate form. The basicity of the quinoid part of phenO(2) in [2](+) and of the diimine one in [Pt(phenO(2)-O,O')(PPh3)(2)] with an O,O'-chelate ring (3) was evaluated in the absence and the presence of Li+ by means of UV-vis spectroscopy and cyclic voltammetry. The quinoid group in [2](+) practically had no ability to bind Li+, but induced on anodic potential shift of the phenO(2) localized redox potential by 850 mV due to the strong interaction between the reduced form of [2](+) and Li+. Undeniably, a weak interaction of Li+ with the diimine moiety of free phenO(2) (K = 3.6 M-1) is greatly enhanced in the interaction between Li+ and the diimine site in 3 because of the electron donation from the catecholato group of the complex.

      DOI: 10.1246/bcsj.79.106

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    • Redox behavior and catalytic oxidation reactions of alcohols by a new ruthenium(III)-dioxolene-amine complex of bis(2-pyridylmethyl)-2-aminoethylamine 査読有り

      Yuji Miyazato, Tohru Wada, Koji Tanaka

      Bulletin of the Chemical Society of Japan79 ( 5 ) 745 - 747   2006年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      A ruthenium-dioxolene-amine complex, [RuIII(NH 2-L)(Bu2sq)](PF6)2·0.5H 2O (NH2-L = bis(2-pyridylmethyl)-2-aminoethylamine, Bu2sq- = 3,5-di-tert-butylsemiquinonate), was newly prepared. The complex undergoes spontaneous one-electron reduction under basic conditions in MeOH and works as an electrocatalyst in the oxidation of benzyl alcohol to benzaldehyde under electrolysis at +0.4 V (vs SCE). © 2006 The Chemical Society of Japan.

      DOI: 10.1246/bcsj.79.745

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    • Novel platinum-ruthenium dinuclear complex bridged by 2-aminoethanethiol. (共著) 査読有り

      Okamura, R, Wada, T, Tanaka, K

      Bull. Chem. Soc. Jpn.79 ( 10 ) 1535 - 1540   2006年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      DOI: 10.1246/bcsj.79.1535

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    • Reversible bond formation and cleavage of the oxo bridge of [Ru2(μ-O)(dioxolene)2(btpyxa)]3+ [btpyxa = 2,7-Di-tert-butyl-9,9-dimethyl-4,5-bis(2,2':6',2''-terpyrid- 4'-yl)xanthene] driven by a three-electron redox reaction 査読有り

      Wada, Tohru, Tanaka, Koji

      European Journal of Inorganic Chemistry19 ( 19 ) 3832 - 3839   2005年10月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley-VCH Verlag GmbH & Co. KGaA  

      The bis(chlororuthenium) complex [Ru2Cl2(3,6-tBu2sq)2(btpyxa)](PF6)2(PF6)2 [3,6-tBu2sq = 3,6-di-tert-butyl-1,2-benzosemiquinone; btpyxa = 2,7-di-tert-butyl-9,9-dimethyl-4,5-bis(2,2':6',2''-terpyrid-4'-yl)xanthene] and the oxobridged diruthenium complex [Ru2(μ-O)(3,6-tBu2sq)2(btpyxa)](PF6)3(PF6)3 were synthesized, and the redox behavior of these complexes, which contain a non-innocent dioxolene ligand, was investigated by electrochem. and electrospectrochem. methods. Dicationic2+ undergoes two successive metal-centered one-electron and a simultaneous two-electron ligand-based redox reaction at E1/2 = +0.13 and +0.09 and E1/2 = -0.75 V (vs. SCE), resp., in CH2Cl2. The UV/Vis/NIR spectrum of tricationic3+ shows an intervalence-transition (IT) band at 1333 nm (ε = 1.52 × 104 M-1 cm-1) in a near-IR region together with two CT bands at 766 (ε = 2.21 × 104 M-1 cm-1) and 586 nm (ε = 1.13 × 104 M-1 cm-1) in CH2Cl2. The mixed-valence complex of3+ with an RuIV-O-RuIII core is reversibly oxidized and reduced to the RuIV-RuIV and RuIII-RuIII oxidn. states at E1/2 = +0.63 and -0.01 V, resp., in CH2Cl2. On the other hand, three-electron redn. of(PF6)3 is accompanied by the cleavage of the Ru-O-Ru bond at Ep = +0.02 V to give [{Ru(OMe)(3,5-tBu2sq)}{Ru(OH2)(3,5-tBu2sq)}(btpyxa)]+ in MeOH.

      DOI: 10.1002/ejic.200500141

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    • Redox behavior of new Ru-dioxolene-ammine complexes and catalytic activity toward electrochemical oxidation of alcohol under mild conditions 査読有り

      T Hino, T Wada, T Fujihara, K Tanaka

      CHEMISTRY LETTERS33 ( 12 ) 1596 - 1597   2004年12月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      The new Ru-dioxolene-ammine complexes, [Ru-II(NH3)-(sq)(trpy)](ClO4) (1, sq = 3,5-di-tert-butyl-1,2-benzoseiniquinone, trpy = 2,2:6,2"-terpyridine) and [Ru-III(NH3)(sq)(trpy)](ClO4)(2) (2), were prepared. They have an ability to oxidize MeOH and i-PrOH catalytically under very mild conditions such as the electrolysis at 0V (vs SCE) in CH2Cl2.

      DOI: 10.1246/cl.2004.1596

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    • A platinum-ruthenium dinuclear complex bridged by bis(terpyridyl)xanthene 査読有り

      R Okamura, T Wada, K Aikawa, T Nagata, K Tanaka

      INORGANIC CHEMISTRY43 ( 22 ) 7210 - 7217   2004年11月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      4,5-Bis(terpyridyl)-2,7-di-tert-butyl-9,9-dimethylxanthene (btpyxa) was prepared to serve as a new bridging ligand via Suzuki coupling of terpyridin-4'-yl triflate and 2,7-di-teil-butyl-9,9-dimethylxanthene-4,5-diboronic acid. The reaction of btpyxa with either 1 equiv or an excess of PtCl2(cod) (cod = 1,5-cyclooctadiene) followed by anion exchange afforded mono- and dinuclear platinum complexes [(PtCl)(btpyxa)](PF6) ([1](PFO) and [(PtCl)(2)(btpyxa)](PF6)(2) ([2]-(PF6)(2)), respectively. The X-ray crystallography of [1](PF6)-CHCl3 revealed that the two terpyridine units in the ligand are nearly parallel to each other. The heterodinuclear complex [(PtCl){Ru((t)Bu(2)SQ)(dmso)}(btpyxa)](PF6)(2) ([4](PF6)(2)) (dmso = dimethyl sulfoxide; (t)Bu(2)SQ = 3,5-di-tert-butyl-1,2-benzosemiquinone) and the monoruthenium complex [Ru((t)Bu(2)SQ)(dmso)(trpy)](PF6) ([5](PF6)) (trpy = 2,2':6',2"-terpyridine) were also synthesized. The CV of [2](2+) suggests possible electronic interaction between the two Pt(trpy) groups, whereas such an electronic interaction was not suggested by the CV of [4](2+) between Pt(trpy) and Ru((t)Bu(2)SQ) frameworks.

      DOI: 10.1021/ic049680n

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    • Strong interaction between carbonyl and dioxolene ligands caused by charge distribution of ruthenium-dioxolene frameworks of mono- and dicarbonylruthenium complexes 査読有り

      T Wada, T Fujihara, M Tomori, D Ooyama, K Tanaka

      BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN77 ( 4 ) 741 - 749   2004年4月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Monocarbonylruthenium complexes with a semiquinone ligand, ([Ru(CO)(sq)(L)(n+) (sq = 3,5-di-tert-butyl-1,2-benzosemiquinone. n = 1 or 0. L = 2,2':6',2"-terpyridine ([1](+)), 2,6-bis(N,N-dimethyIaminomethyl)pyridine ([2](+)), 2.6-di-2'-pyridylphenyl ([3](0)), or 2-(2,2'-bipyridin-6-yl)phenolato ([4](0))), and dicarbonylruthenium complexes with two semiquinone ligands, [Ru(CO2)(2)(sq)(2)] ([5](0)) and [Ru(CO)(2)(phsq)(2)] (phsq = 9,10-phenanthrasemiquinone, [6](0)), were synthesized and the structures of [1](+) and [6] were determined by X-ray crystal analysis. Monocarbonyl Ru(II)-dioxolene complexes displayed the ligand localized catecholato/semiquinone and semiquinone/quinone redox couples, and two sets of those redox couples were observed in the dicarbonyl Ru(II)-bis(dioxolene) complexes. Spectroelectrochemical study revealed that the Ru(II)-catecholato and Ru(II)-semiquinone complexes were stable in solutions, while the Ru(II)-quinone complexes underwent fragmentation in solutions. One-electron reduction of the rnonocarbonyl Ru(II)- was substantially larger semiquinone complexes caused a red shift of the nu(CO) bands in a range of 41 to 56 cm(-1), which was substantially larger than those of carbonyl Ru(II)-polypyridyl complexes. Two nu(CO) bands of dicarbonyl Ru(II)-bis(semiquinone) complexes also shifted to lower wavelength in a range of 53 to 99 cm(-1) upon two electron reduction of the complexes. The unusually large red shift of nu(CO) bands upon reduction of carbonyl Ru(II)-dioxolene complexes compared with those of Ru(II)-polypyridyl complex is ascribed to a strong electronic interaction between carbonyl and dioxolene ligands.

      DOI: 10.1246/bcsj.77.741

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    • Syntheses and electrochemical properties of ruthenium(II) complexes with 4,4 '-bipyrimidine and 4,4 '-bipyrimidinium ligands 査読有り

      T Fujihara, T Wada, K Tanaka

      INORGANICA CHIMICA ACTA357 ( 4 ) 1205 - 1212   2004年3月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

      The syntheses and electrochemical properties of novel ruthenium(II) polypyridyl complexes with 4,4'-bipyrimidine, [Ru(trpy)(bpm)Cl](X) ([1](X; X = PF6-, BF4-)) and with a quaternized 4,4'-bipyrimidinium ligand, [Ru(trpy)(Me(2)bpm)Cl](BF4)(3) ([2](BF4)3) (trpy = 2,2':6',2"-terpyridine, bpm = 4,4'-bipyrimidine, Me(2)bpm = 1,1'-dimethyl-4,4'-bipyrimidinium) are presented. The bpm complex [1](divided by) was prepared by the reaction of Ru(trpy)Cl-3 with 4,4'-bipyrimidine in EtOH/H2O. The structural characterization of [1](divided by) revealed, that the bpm ligand coordinated to the ruthenium atom with the bidentate fashion. Diquaternization of the noncoordinating nitrogen atoms on bpm of [1](divided by) by (CH3)(3)OBF4 in CH3CN gave [2](BF4)(3). The electrochemical and spectroelectrochemical properties of the complexes are described. (C) 2003 Elsevier B.V. All rights reserved.

      DOI: 10.1016/j.ica.2003.10.015

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    • Acid-base equilibria of various oxidation states of aqua-ruthenium complexes with 1,10-phenanthroline-5,6-dione in aqueous media 査読有り

      T Fujihara, T Wada, K Tanaka

      DALTON TRANSACTIONS ( 4 ) 645 - 652   2004年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

      Syntheses and pH dependent electrochemical properties of aqua-ruthenium(II) complexes, [Ru(trpy)(PDA-N,N')-(OH2)](ClO4)(2) ([1](ClO4)(2)) and [Ru(trpy)(PD-N,N')(OH2)](ClO4)(2) ([2](ClO4)(2)) (trpy = 2,2':6',2"-terpyridine, PDA = 6-acetonyl-6-hydroxy-1,10-phenanthroline-5-one, PD = 1,10-phenanthroline-5,6-dione) are presented. Treatment of [Ru(trpy)(PD-N,N')Cl](PF6) with AgClO4 in a mixed solvent of acetone and H2O selectively produced the acetonyl-PD complex [1](ClO4)(2), and the similar treatment in a mixed solvent of 2-methoxyethanol and H2O gave the PD complex[2](ClO4)(2). The molecular structures of both complexes were determined by X-ray structural analysis. The proton dissociation constants of various oxidations state of [1](2+) and [2](2+) were evaluated by simulation of E-1/2 values of those redox potentials depending on pH. The simulation revealed that the acetonyl-PD complex[1](2+) underwent successive Ru(II)/Ru(III) and Ru(III)/Ru(IV) redox couples though the two redox reactions were not separated in the cyclic voltammograms. The redox behavior of [2](2+) in H2O is reasonably explained by not only the similar successive metal-centered redox reactions but also simultaneous two-electron quinone/catechol redox couple of the PD ligand including the contribution of hydration on a carbonyl carbon.

      DOI: 10.1039/b312310c

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    • Coordination ability of 1,10-phenanthroline-5,6-dione: syntheses and redox behavior of a Ru(II) complex with an o-quinoid moiety and of bridged Ru(II)-M(II) complexes (M = Pd, Pt) 査読有り

      T Fujihara, R Okamura, T Wada, K Tanaka

      DALTON TRANSACTIONS ( 16 ) 3221 - 3226   2003年8月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

      The synthesis and electrochemical properties of a Ru(II) complex having a redox active ligand, 1,10-phenanthroline-5,6-dione, [Ru(trpy)(PD-N,N')Cl](PF6) ([1](PF6)), and mixed-metal complexes [(PPh3)(2)Pd(O,O'-PD-N,N')Ru(trpy)-Cl](PF6) ([2](PF6)) and [(PPh3)(2)Pt(O,O'-PD-N,N')Ru(trpy)Cl](PF6) ([3](PF6)) (trpy = 2,2':6',2"-terpyridine, PD = 1,10-phenanthroline-5,6-dione) are presented. The complex of [1](+), which was prepared by the reaction of Ru(trpy)(DMSO)Cl-2 with PD in hot ethanol, underwent two reversible reductions in the PD-based redox reactions. The quinoid moiety of [1](+) was endowed with coordination ability to metals by one- and two-electron reduction of the complex. The mixed-metal complexes of [2](+) and [3](+) were synthesized by the reactions of [1](+) with M(PPh3)(4) (M = Pd, Pt), and both complexes have the [1](-) and M(II) frameworks.

      DOI: 10.1039/b304912d

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    • Characterization of a stable ruthenium complex with an oxyl radical 査読有り

      K Kobayashi, H Ohtsu, T Wada, T Kato, K Tanaka

      JOURNAL OF THE AMERICAN CHEMICAL SOCIETY125 ( 22 ) 6729 - 6739   2003年6月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      The ruthenium oxyl radical complex, [Ru-II(trpy)(Bu(2)SQ)O.-] (trpy = 2,2':6',2"-terpyridine, Bu-2-SQ = 3,5-di-tert-butyl-1,2-benzosemiquinone) was prepared for the first time by the double deprotonation of the aqua ligand of [Ru-III(trpy)(Bu(2)SQ)(OH2)](ClO4)(2), [Ru-III(trpy)(BU2SQ)(OH2)](ClO4)(2) is reversibly converted to [Ru-III(trpy)(Bu(2)SQ)(OH-)](+) upon dissociation of the aqua proton (pK(a) 5.5). Deprotonation of the hydroxo proton gave rise to intramolecular electron transfer from the resultant O2- to Ru-dioxolene. The resultant [Ru-II(trpy)(Bu(2)SQ)O.-] showed antiferromagnetic behavior with a Ru-II-semiquinone moiety and oxyl radical, the latter of which was characterized by a spin trapping technique. The most characteristic structural feature of [Ru-II(trpy)(Bu(2)SQ)O.-] is a long Ru-O bond length (2.042(6) Angstrom) as the first terminal metal-O bond with a single bond length. To elucidate the substituent effect of a quinone ligand, [Ru-III(trpy)(Bu(2)SQ)(OH2)](ClO4)(2) (4CISQ = 4-chloro-1,2-benzosemiquinone) was prepared and we compared the deprotonation behavior of the. aqua ligand with that of [Ru-III(trpy)(Bu(2)SQ)(OH2)](ClO4)(2). Deprotonation of the aqua ligand of [Ru-III(trpy)(4CISQ)(OH2)](ClO4)(2) induced intramolecular electron transfer from OH- to the [Ru-III-(4CISQ)] moiety affording [Ru-II(trpy)(4CISQ)(OH.)](+), which then probably changed to [Ru-II(trpy)(4CISQ)O.-]. The antiferromagnetic interactions. (J values) between Ru-II-semiquinone and the oxyl radical for [Ru-II(trpy)(Bu(2)SQ)O.-] and for [Ru-II(trpy)(4CISQ)O.-] were 2J = -0.67 cm(-1) and -1.97 cm(-1), respectively.

      DOI: 10.1021/ja0211510

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    • Ruthenium oxyl radical complex containing o-quinone ligand detected by ESR measurements of spin trapping technique 査読有り

      K Kobayashi, F Ohtsu, T Wada, K Tanaka

      CHEMISTRY LETTERS ( 8 ) 868 - 869   2002年8月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Ruthenium-quinone complex containing an aqua ligand, [Ru-II(trpy)(35tBu(2)Q)(OH2)](ClO4)(2) (trpy=2,2':6',2"-terpyridine, 35tBu(2)Q=3,5-di-tert-butyl-1,2-benzoquinone) underwent deprotonation of an aqua ligand accompanied with intramolecular electron transfer from O2- ligand to quinone ligand generating O.- ligand.

      DOI: 10.1246/cl.2002.868

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    • Novel diruthenium disulfinate complex formed by oxygen capture on deprotonated form of ruthenium-aqua-dithiolene: Four oxygens from O-2 and four oxygens from H2O 査読有り

      H Sugimoto, H Wada, Y Wakatsuki, T Wada, K Tanaka

      CHEMISTRY LETTERS ( 6 ) 634 - 635   2002年6月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Oxygenation of sulfur in ruthenium-dithiolene complex took place in CH3OH/H2O in the air and the novel diruthenium disulfinate complex formed. The similar oxygenation by use of O-18(2) and H-2 O-18 revealed that four of the eight oxygen of disulfinate complex resulted from O-2 and the remaining four came from H2O.

      DOI: 10.1246/cl.2002.634

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    • A Ru-carbene complex with a metallacycle involving a 1,8-naphthylidine framework 査読有り

      T Tomon, D Ooyama, T Wada, K Shiren, K Tanaka

      CHEMICAL COMMUNICATIONS ( 12 ) 1100 - 1101   2001年6月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

      The reaction of [Ru(bpy)(2)(napy-kappa N-2,N')](PF6)(2) [1](PF6)(2) (napy = 1,8-naphthyridine) with propiolic acid yielded a Ru-carbene complex with a five-membered metallacycle involving a 1,8-naphthylidine framework.

      DOI: 10.1039/b101045j

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    • Studies on Bis(hydroxoruthenium)complexes with Quinones as Non-innocent Ligands and Their Catalytic Abilities for Oxidation Reactions 査読有り

      Tohru Wada

          2001年3月20日

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      記述言語:英語   掲載種別:学位論文(博士)  

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    • Platinum-catalyzed bis-germylation of alkynes with organodigermanes and cyclic oligogermanes 査読有り

      K Mochida, T Wada, K Suzuki, W Hatanaka, Y Nishiyama, M Nanjo, A Sekine, Y Ohashi, M Sakamoto, A Yamamoto

      BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN74 ( 1 ) 123 - 137   2001年1月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Hexamethyldigermane, Me3CeGeMe3, reacted with various alkynes in the presence of platinum complexes at 120 degreesC to afford Z-1,2-bis(germyl)ethenes in moderate to good yields. Terminal alkynes exhibit higher reactivities than internal ones. [Pt(acac)(2)] and [Pt(dba)(2)] serve as efficient catalysts, while [Pt(PPh3)(4)], [PtCl2(PPh3)(2)], and [Pt(dba)(2)]-phosphite were found to be inactive. Four- and six-membered cyclic oligogermanes, such as dodecamethylcyclohexagermane. (Me2Ge)(6), reacted with alkynes in the presence of platinum catalysts to yield 1,4-digermacyclohexa-2,5-dienes in ca. 30% yield. The reactions of phenylacetylene with 1,2-digermacyclohexa-3,5-dienes afforded the corresponding 1,4-digermacyclohexa-2,5,7-trienes in 93% yield. Bis(germyl)platinum complexes having various tertiary phosphine ligands have been prepared as models of a key intermediate in the above mentioned catalytic bis-germylation of alkynes, and their structures have been established by spectroscopic methods and X-ray crystallography. Bis(germyl)platinum complexes reacted with phenylacetylene to give the corresponding insertion products, germyl(germylvinyl)platinum species, whose structures have been determined by spectroscopic and X-ray analysis. Germyl(germylvinyl)platinum complexes were found to liberate a bis-germylation product of the alkyne upon heating. The result supports a mechanism involving the oxidative addition of a digermane to a Pt(0) complex, the insertion of an alkyne into one of the two Pt-Ge bonds to give a germyl(germylvinyl)platinum species, and the reductive elimination of the bis-germylation product of the alkyne. Evidence suggesting the extrusion of a germylene unit from the bis-germylplatinum species has been obtained, accounting for the generation courses of other by-products.

      DOI: 10.1246/bcsj.74.123

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    • Syntheses and redox properties of bis(hydroxoruthenium) complexes with quinone and bipyridine ligands. Water-oxidation catalysis 査読有り

      T Wada, K Tsuge, K Tanaka

      INORGANIC CHEMISTRY40 ( 2 ) 329 - 337   2001年1月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

      The novel bridging ligand 1,8-bis(2,2':6',2"-terpyridyl)anthracene (btpyan) is synthesized by three reactions from 1,8-diformylanthracene to connect two [Ru(L)(OH)](+) units (L = 3,6-di-tert-butyl-1,2;benzoquinone (3,6-Bu-t(2)-qui) and 2,2'-bipyridine (bpy)). An addition of (BuOK)-Bu-t (2.0 equiv) to a methanolic solution of [Ru-2(II)(OH)(2)(3,6-(t)Bu(2)qui)(2)(btpyan)](SbF6)(2) ([1](SbF6)(2)) results in the generation of [Ru-2(II)(O)(2)(3,6-(t)Bu(2)sq)(2)(btpyan)](0) (3,6-(t)Bu(2)sq = 3,6 -di-tert-butyl-1,2-semiquinone) due to the reduction of quinone coupled with the dissociation of the hydroxo protons. The resultant complex [Ru-2(II)(O)(2)(3,6-(t)Bu(2)sq)(2)(btpyan)](0) undergoes ligand-localized oxidation at E-1/2 = +0.40 V (vs Ag/AgCl) to give [Ru-2(II)(O)(2)(3,6-(t)Bu(2)qui)(2)(btpyan)](2+) in MeOH solution: Furthermore, metal-localized oxidation of [Ru-2(II)(O)(2)(3, 6-(t)Bu(2)qui)(2)(btpyan)](2+) at E-p = + 1.2 V in CF3CH2OH/etheq or water gives [Ru-2(III)(O)(2)(3,6-(t)Bu(2)qui)(2)(btpyan)](4+), which catalyzes water oxidation. Controlled-potential electrolysis of [1](SbF6)(2) at +1.70 V in the presence of H2O in CF3CH2OH evolves dioxygen with a current efficiency of 91% (21 turnovers). The turnover number of O-2 evolution increases to 33 500 when the electrolysis is conducted in water (pH 4.0) by using a [1](SbF6)(2)-modified ITO electrode. On the other hand, the analogous complex [Ru-2(II)(OH)(2)(bpy)(2)(btpyan)](SbF6)(2) ([2](SbF6)(2)) shows neither dissociation of the hydroxo protons, even in the presence of a large excess of (BuOK)-Bu-t, nor activity for the oxidation of H2O under similar conditions.

      DOI: 10.1021/ic000552i

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    • Preparation and reductive elimination of digermylplatinum complexes 査読有り

      Kunio Mochida, Tohru Wada, Wakako Hatanaka, Yuriko Nishiyama, Michiko Suzuki, Masato Nanjo

      Main Group Metal Chemistry24 ( 9 ) 647 - 652   2001年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Walter de Gruyter GmbH  

      cis- and trans-(R3Ge)2Pt(PMe2Ph)2 complexes as key intermediates of bis-germylation of alkynes have been prepared, and their structures have been established by spectroscopic methods and X-ray crystallography. The cis isomers afford digermanes, (R3Ge)2 as reductive elimination products in good yields. In contrast, the trans isomers lead to monogermanes.

      DOI: 10.1515/MGMC.2001.24.9.647

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    • Oxidation of hydrocarbons by mono- and dinuclear ruthenium quinone complexes via hydrogen atom abstraction 査読有り

      T Wada, K Tsuge, K Tanaka

      CHEMISTRY LETTERS ( 8 ) 910 - 911   2000年8月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      Deprotonation and two-electron oxidation of [Ru-2(II)(OH)(2)(Q)(2)(btpyan)](2+) (Q = 3,6-di(tert-butyl)-1,2-quinone, btpyan = 1,8-bis(2,2':6',2"-terpyridyl)anthracene) was converted to bis(ruthenium-oxo) complex [Ru-2(II)(O)(2)(Q)(2)(btpyan)](2+), which oxidized 1,3-cychrohexadiene and 1,2-dihydronaphtalene to corresponding aromatic compounds in the presence of AgClO4 and t-BuOK. On the other hand, mononuclear complex [Ru-II(OH2)(Q)(Ph-terpy)](2+) (Ph-terpy = 4'-phenyl-2,2': 6',2"-terpyridine, [2](2+)) was converted to [Ru-II(OH)(Q)(Ph-terpy)](2+) under the similar conditions, but displayed the low activity for the oxidation compared with the dinuclear complex [1](2+).

      DOI: 10.1246/cl.2000.910

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    • Electrochemical oxidation of water to dioxygen catalyzed by the oxidized form of the bis(ruthenium-hydroxo) complex in H2O 査読有り

      T Wada, K Tsuge, K Tanaka

      ANGEWANDTE CHEMIE-INTERNATIONAL EDITION39 ( 8 ) 1479 - +   2000年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

      Electrochem. oxidn. of water is catalyzed by an ITO electrode modified with a bis(ruthenium-hydroxo) complex. This ruthenium complex is prepd. by reacting RuCl3 with 1,8-bis(terpyridyl)anthracene (btpyan) in MeOH, treating [Ru2Cl6(btpyan)] with 3,6-di-tert-butyl-1,2-benzenediol in the presence of KOAc in MeOH. This [RuII 2(OAc)(3,6-tBu2sq)2(btpyan)]+ (3,6-tBu2sq = 3,6-di(tert-butyl)-1,2-semiquinone) was treated with triflic acid in MeOH contg. water and then sodium hexafluoroantimonate to give [Ru2(OH)2(3,6-tBu2qui)2(btpyan)](SbF6)2. When a controlled-potential electrolysis for this complex on ITO electrode was conducted at +1.7 V (vs. Ag/AgCl) in water, 1.1 mL of O2 evolved after 20.2 C had passed in the electrolysis. The current efficiency for O2 evolution was 95%.

      DOI: 10.1002/(SICI)1521-3773(20000417)39:8<1479::AID-ANIE1479>3.0.CO;2-4

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    • Thermal ring contraction of 1,2-digermacyclohexadienes coordinated with iron tricarbonyl fragment 査読有り

      K Mochida, W Hatanaka, T Wada, A Sekine, Y Ohashi, A Yamamoto

      CHEMISTRY LETTERS ( 10 ) 991 - 992   1998年10月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

      1, 1, 2, 2-Tetraalkyl-3, 6-diphenyl-1, 2-digermacyclohexa-3, 5-dienes (1) reacted with iron pentacarbonyl to give the corresponding tricarbonyl(eta(4)-1,1,2,2-tetraalkyl-3,6-diphenyl-1,2-digermacyclohexa-3,5-diene)iron (2). Heating 2 caused extrusion of dialkylgermylenes to give (eta(4)-1,1-dialkyl-2,5-diphenyl-1-germacyclopenta-2,4-diene)tricarbonyliron (3). The structures of the (diene)iron tricarbonyls were determined by X-ray crystal structure analysis.

      DOI: 10.1246/cl.1998.991

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    書籍等出版物

    • Molecular Water Oxidation Catalysis

      Wada, Tohru, Tanaka, Koji, Muckerman, James T, Fujita, Etsuko( 担当: 共著)

      John Wiley & Sons Ltd.  2015年  ( ISBN:9781118413371

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      記述言語:英語 著書種別:学術書

      This article discusses about the water oxidn. catalyzed by dinuclear ruthenium catalysts with non-innocent ligands. Describe electrocatalytic water oxidn. by the Tanaka catalyst and a related [Ru2(μ-Cl(bpy)2(btpyan))]3+ ([1Cl(bpy)2]3+), which is a precatalyst of the water oxidn. catalyst [Ru2 III(OH)2(bpy)2(btpyan)]4+ ([(OH)2(bpy)2]4+), then explain the acid-base equil. and redox behavior of mononuclear Ru-aqua complexes with a variety of dioxolene ligands, since a dioxolene ligand on the ruthenium has substantial effects on the electronic state and catalytic activity of the ruthenium complexes.

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    • 実験化学講座22巻—金属錯体、遷移金属錯体クラスター−

      和田 亨, 田中 晃二( 担当: 共著)

      丸善  2004年  ( ISBN:4621073214

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      記述言語:日本語 著書種別:事典・辞書

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    所属学協会

    共同研究・競争的資金等の研究

    • 二核構造を基盤とした遷移金属錯体触媒による光化学的二酸化炭素還元反応

      日本学術振興会  科学研究費助成事業 基盤研究(C) 

      和田 亨

      詳細を見る

      2021年4月 - 2024年3月

      課題番号:21K05102

      配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

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    • 天然の光合成の仕組みを模倣したルテニウム酸素発生触媒の開発

      日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型) 

      和田 亨

      詳細を見る

      2020年4月 - 2022年3月

      課題番号:20H05116

      配分額:6500000円 ( 直接経費:5000000円 、 間接経費:1500000円 )

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    • Pt(II)/Pt(IV)酸化還元対を活用した新規な還元反応触媒系の構築

      日本学術振興会  科学研究費助成事業 基盤研究(C) 

      和田 亨

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      2018年4月 - 2021年3月

      課題番号:18K05158

      担当区分:研究代表者  資金種別:競争的資金

      配分額:4290000円 ( 直接経費:3300000円 、 間接経費:990000円 )

      一般的に、Pt(II)錯体は四配位平面正方型を、Pt(IV)錯体は六配位八面体型の構造を好む。Pt(II)/Pt(IV)の酸化還元には大きな構造変化を伴い、非常に大きなエネルギーを必要とすることから、通常の白金錯体は酸化還元不活性である。ところが、環状三座配位子である1,4,7ートリアザシクロノナン(tacn)を有する白金錯体は、tacnの可逆な構造変化が伴うことによって、Pt(II)/Pt(IV)の可逆な酸化還元が可能である。本研究課題ではPt(tacn)錯体のPt(II)/Pt(IV)酸化還元対を活用した新規還元反応を開発することを目的としている。本年度は、[PtX(tacn)(bpy)]3+ (X = Cl, Br, I, bpy = 2,2'-ビピリジン)を合成、その酸化還元挙動を詳細に検討し、配位子Xが酸化還元挙動に与える影響について明らかにした。その結果、Pt(IV)からPt(II)への二電子還元過程と、Pt(II)からPt(IV)への二電子酸化過程が異なる経路で進行することを解明した。さらに、[PtCl(tacn)(bpy)]3+ を亜鉛で還元することにより、平面正方型のPt(II)錯体である[Pt(tacn)(bpy)](PF6)2を良好な収率で単離することに成功した。これまでは[PtCl(tacn)(bpy)]3+ を電気化学的に還元した後に、再結晶化することによって数粒の[Pt(tacn)(bpy)](PF6)2を得るのが精一杯であったが、新たな合成方法を確立したことにより、還元体[Pt(tacn)(bpy)]2+を実用的な収率で単離できた。還元反応の鍵となるPt(II)錯体の性質と反応性を解明することにより、触媒的な還元反応の研究に大きな進展がもたらされると考える。

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    • 光合成のPCET機能を模倣したルテニウム錯体による高効率光酸素発生系の構築

      日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型) 

      和田 亨

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      2018年4月 - 2020年3月

      課題番号:18H05179

      配分額:5200000円 ( 直接経費:4000000円 、 間接経費:1200000円 )

      天然の光合成では、Photosystem IIに存在するマンガンとカルシウム、酸素から構成されるクラスターが水の酸化反応を触媒している。近年、Photosystem IIの高精度の結晶構造解析が報告され、このマンガンクラスターが近傍に存在するチロシン残基と水素結合していることが明らかにされた。チロシン残基のフェノールは、光増感の役割をしているクロロフィルP640とマンガンクラスターとの間の電子移動に重要な役割をしている。本研究では、この天然光合成におけるチロシン残基がマンガンクラスターの酸素発生触媒活性の向上に関わっているとの予想に基づき、人工的な水の酸化触媒であるルテニウム錯体にフェノール基を導入した新規錯体触媒[Ru(OH2)(bpy)(thaq)]2+ (bpy = 2,2'-ビピリジン、thaq = 1,8-(2,4-ジ-tert-ブチルヒドロキシフェニル)アントラキノン)を合成した。平衡電極電位近傍での電気化学的な水の酸化反応を実現すると共に、水の酸化反応におけるフェノール部位の役割を明らかにすることを目的とする。本反応系におけるフェノール部位の役割を解明することは、天然の光合成の反応機構解明にも寄与するものと考えている。[Ru(OH2)(bpy)(thaq)](PF6)2を電極上に塗布して作成した修飾電極を用いて電気化学的な水の酸化反応について検討を行ったところ、フェノール部位を持たない錯体触媒に比べて、150 mV小さい過電圧で3.5倍の反応速度を達成した。水溶性の向上を目指し、bpy上にカルボキシ基を導入した水溶性錯体触媒を合成した。10%のトルフルオロエタノールと水の混合溶液中でのCVから、[Ru(OH2)(bpy)(thaq)]2+と同等の触媒活性を示すことがわかった。また、ESR測定により重要な中間体であるフェノキシルラジカル種の生成を確認した。

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    • 光合成酸素発生中心の機能を模倣した二核ルテニウム錯体による水の酸化反応

      日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型) 

      和田 亨

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      2015年4月 - 2017年3月

      課題番号:15H00884

      配分額:3900000円 ( 直接経費:3000000円 、 間接経費:900000円 )

      本研究課題では人工光合成のボトルネックといわれる水の四電子酸化反応を、平衡電極電位(+1.23 V vs.NHE, pH0)よりも+100mVから+200 mV程度の過電圧で進行させる小過電圧触媒系の実現を目指し、光合成の仕組みを模倣した人工系二核ルテニウム錯体触媒の開発を行った。天然の光合成では、酸素発生中心であるマンガンクラスターの近傍に存在するチロシン残基が電子とプロトンの移動に重要な役割を担っている。本研究ではOECを模倣して、チロシンと同じフェノール骨格を分子内に有する二核ルテニウム錯体の合成について検討した。当初は架橋部位をアントラセノールとした二核化配位子の合成を目指し、多くの合成経路について検討したが、実用的な収率に至らなかった。そこで、アントラセンの1位にルテニウムを結合するターピリジル基、8位にヒドロキシフェニル基を有する配位子の合成を検討した。最終的に、アントラセン-1,8-ジボロン酸とトリフルオロメタンスルホニルターピリジン及びブロモアニソールのワンポット鈴木ー宮浦クロスカップリング反応で良好な収率で合成に成功した。この配位子を用いて単核ルテニウム錯体を合成し、その構造を単結晶X-線構造解析で明らかにした。さらに合成した錯体のCVを測定し、水の酸化に対して触媒活性を示すことがわかった。有機溶媒中ではフェノール部位の不可逆な酸化波が+1.2V(vs. SCE)に観測され、水中ではこの電位近辺から水の酸化に由来する触媒電流が生じた。現在、フェノール部位が水の酸化に与える影響と反応機構について検討を行っている。さらに、非常に強い電子供与性の配位子を有するルテニウム錯体が、小過電圧で水の酸化を触媒することを明らかにした。二核ルテニウム錯体触媒に夜水の酸化反応については、反応活性種が[Ru(IV)=O O=Ru(V)]である明確な証拠を得た。

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    • 光合成酸素発生中心の仕組みを組み込んだ複核ルテニウム錯体による水の酸化反応

      日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型) 

      和田 亨

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      2013年4月 - 2015年3月

      課題番号:25107524

      配分額:3640000円 ( 直接経費:2800000円 、 間接経費:840000円 )

      光合成酸素発生中心(Oxygen evolving center, OEC)では、水の酸化による酸素発生反応を触媒するマンガンクラスターに水素結合したチロシン残基が存在しており、電子とプロトンの伝達に重要な役割をしている。本研究では、すでに研究代表者らが開発している二核ルテニウム構造を有する水の酸化触媒に、チロシン残基を模倣した酸化還元活性な架橋配位子を導入することより、より高活性な水の酸化触媒系を構築することを目的とする。
      酸化還元活性な架橋配位子として二つのターピリジンをアントラセノールでつないだ新規配位子、ビス(ターピリジル)アントラセノールの合成について検討した。1,8-ジクロロアントラキノンから4段階の反応を経て合成が可能であることを明らかにした。収率の向上にむけて検討を継続している。また、別途に新規架橋配位子ビス(ターピリジル)アントラキノン(btpyaq)を用いた二核ルテニウム錯体を合成した。このアントラキノン架橋錯体を触媒に用いると、対応するアントラセン架橋錯体を触媒に用いたときに比べ、水の酸化の反応速度が向上することが明らかとなった。この結果は、架橋部位のアントラキノンのカルボニル基が親水性基として働き、酸素分子と水分子の置換反応が促進されたためだと考えられる。また、電子供与性が非常に強い配位子であるジピリジルフェニル基を有する単核ルテニウム錯体を合成したところ、対応するターピリジン錯体と比較して720mVもの酸化還元電位の負電位シフトが観測された。穏やかな酸化剤である[Ru(bpy)3]3+ (bpy = ビピリジン)を用いて水の酸化反応を行ったところ酸素発生が確認された。これらの結果より触媒設計に於いて、電位を低下し反応速度を向上させるための要素を明らかにすることが出来た。

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    • エネルギー変換を指向した酸素発生錯体触媒の開発

      日本学術振興会  科学研究費助成事業 基盤研究(C) 

      和田 亨

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      2011年 - 2013年

      課題番号:23550084

      配分額:5330000円 ( 直接経費:4100000円 、 間接経費:1230000円 )

      本研究では、人工光合成の実現に欠かすことができない水の4電子酸化反応を熱力学の平衡電位付近で行うことを目的とし、単核および二核錯体触媒の開発を行った。テトラメチルエチレンジアミン(tmen)やジピリジルベンゼン(dpb)などの非常に強い電子供与性配位子を導入したルテニウム錯体を触媒として用いると、平衡電極電位近辺の電位で水の酸化が進行することが明らかとなった。さらに酸化物固体と錯体のハイブリッド触媒の開発を目指し、リン酸基を有する二核ルテニウム錯体を合成した。この二核錯体をITO電極上に結合し、酸化還元挙動を明らかにした。

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    • 高活性酸素発生触媒の開発

      日本学術振興会  科学研究費助成事業 若手研究(B) 

      和田 亨

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      2008年 - 2009年

      課題番号:20750123

      配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

      エネルギー環境問題の観点から大きな注目を集める水の四電子酸化反応を触媒する2核ルテニウム錯体を開発した。Ce(IV)酸化剤存在下、この二核ルテニウム錯体は水を酸化し酸素を高効率で発生した。反応過程を詳細に分析する事により2分子の水から酸素-酸素結合が形成されることを明らかにした。

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    • エネルギー変換を指向した水およびアンモニアの酸化的活性化触媒の開発

      日本学術振興会  科学研究費助成事業 特定領域研究 

      和田 亨

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      2007年

      課題番号:19028064

      配分額:2000000円 ( 直接経費:2000000円 )

      遷移金属錯体に配位したラジカル種は生体内の酵素反応の活性中心にみられ、その反応性に注目が集まっている。我々はこれまでにRu^<III>(3,5-t-Bu_2sq)(3,5-t-Bu_2sq=3,5-ジ-tert-ブチル-1,2-ベンゾセミキノン)骨格上に配位した水分子がプロトンを解離することにより、容易にオキソ配位子上に不対電子を誘起したオキシルラジカル錯体[Ru^<II>(O^<-.>)(3,5-t-Bu_2sq)(terpy)]を生成することを報告している。今回、同様のRu^<III>(3,5-t-Bu_2sq)骨格に四座配位子NH_2-bpa(NH_2-bpa=ビス(2-ピリジルメチル)-2-アミノエチルアニリン)を導入することにより、安定なアニリノラジカル錯体の合成と同定に成功した。[Ru^<III>(NH-bpa)(3,5-t-Bu_2sq)]^+は872nmと1172nmに特徴的な吸収を示すが、これらはそれぞれルテニウム-セミキノン間、ルテニウム-アニリド間のMLCTに帰属される。ジメトキシエタン中、[Ru^<III>(NH-bpa)(3,5-t-Bu_2sq)]^+に対して1等量のt-BuOKを作用させるとアニリドプロトンが解離しアニリノラジカル錯体[Ru^<III>(^-N-bpa)(3,5-t-Bu_2sq)]^0を生成する。[Ru^<III>(^-N-bpa)(3,5-t-Bu_2sq)]^0のEPRを測定するとΔM_s=2の遷移基づくシグナルがg=4.2に観測されたことから、S=1の三重項状態であることが分かった。さらに[Ru^<III>(^-N-bpa)(3,5-t-Bu_2sq)]^0を電気化学的に一電子還元することにより生成した[Ru^<III>(^-N-bpa)(3,5-t-Bu_2cat)]^<-1>(cat=カテコール)のEPRシグナルには、N原子のハイパーファインカップリングが観測された。セミキノン-アニリノラジカル錯体[Ru^<III>(^-N-bpa)(3,5-t-Bu_2sq)]^0とカテコラト-アニリノラジカル錯体[Ru^<III>(^-N-bpa)(3,5-t-Bu_2cat)]^<-1>に対してDFT計算を行うと、前者では電子スピンが非局在化しているのに対して、後者ではN-bpa上にほぼ局在化していることが分かった。これまでにアニリノラジカル錯体の報告はあるが、いずれも酸化剤を用いているのに対して、本反応系では酸塩基平衡のみを駆動力としてラジカル種を誘起している。この様な穏和な条件でのラジカル生成は酵素活性中心の機能解明のみならず、新たな触媒反応への展開が可能である。

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    • 可視光エネルギーを利用した水の酸化触媒の開発

      日本学術振興会  科学研究費助成事業 若手研究(B) 

      和田 亨

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      2006年 - 2007年

      課題番号:18750126

      配分額:3500000円 ( 直接経費:3500000円 )

      二核化配位子1,8-ビス(ターピリジル)アントラセン(btpyan)を用いて、(3,6-t-Bu_2q)Ru(OH)(3,6-t-Bu_2q=3,6-ジ-tert-ブチル-1,2-ベンゾキノン)部位を向かい合わせに架橋した[Ru_2(OH)_2(3,6-t-Bu_2q)_2(btpyan)](SbF_6)_2は水の四電子酸化による酸素発生反応を効率よく触媒する。ジオキソレン配位子上の置換基は触媒活性に大きく影響し、3,6-t-Bu基の代わりに4-NO_2,3,5-Cl_2が置換した錯体では酸素発生反応に対する触媒活性を示さなかった。そこで、錯体の電子状態に対するジオキソレン配位子上の置換基効果を明らかにするため、一連の[Ru(OAc)(L)(terpy)]錯体(L=3,5-t-Bu_2C_6H_2O_2,4-t-BuC_6H_3O_2,4-ClC_6H_3O_2,3,5-Cl_2C_6H_2O_2,Cl_4C_6O_2,terpy=2,2':6',2"-ターピリジン)を合成し、その電子状態をEPRで検討したところRu(L)部位はRu^<II>(sq)(sq=semiquinone)とRu^<III>(cat)(cat=catecholato)の中間的な電子状態をとり、置換基の電子供与性が増加するほどRu^<II>(sq)に、電子吸引性が大きいほどRu^<III>(cat)に近いことが明らかになった。DFT計算を用いて、酸素発生反応の機構に関して検討を行ったところ、[Ru_2(OH)_2(3,6-t-Bu_2q)_2(btpyan)]^<2+>は二つのプロトンを解離することにより分子内でラジカル的にO-O結合を形成することが示唆された。また興味深いことに、酸素発生に必要な四電子の酸化を錯体内の中心金属であるルテニウムではなく、ジオキソレン配位子が担っていることが分かった。これらの結果はこれまでに提唱されていない全く新しい酸素発生機構であり、同研究領域に大きな影響を与えるものと考えられる。

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    産業財産権

    • 金属錯体およびこれを含む燃料電池用カソード

      和田亨

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      出願番号:特願2013-121811  出願日:2013年6月10日

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    • ルテニウム三価アンミン錯体化合物

      日野貴美, 和田亨, 田中晃二

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      公開番号:4212411  公開日:2008年11月7日

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    学術貢献活動

    • カーボン・エネルギーコントロール社会協議会

      石谷治・工藤昭彦・民秋均 

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      種別:その他 

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    社会貢献活動

    • 化学の未来を創る女子中高生のチャレンジラボ

      講師, 企画

      2018年6月1日 - 2020年3月31日

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      種別:出前授業

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